How to manage long journeys as DM

I recently started running Hoard of the Dragon Queen as a DM and this is the first time for me. During the campaign there are a lot of journeys that take several days, even weeks, and in some cases nothing important happens. Now, my question is: how much time should I dedicate to them? Should I just say "You travel from A to B in X days", maybe adding some details about the road, or should I provide a longer and more detailed description? The same question holds when some important events are planned: should I move directly from one event to the other, like "two days after event A, event B occurs"? I read the advices in the DMG but I would like to have more specific indications on the typical approach. Also, I am afraid that if I start describing some elements of the environment (a waterfall, a big rock, a tree and so on) then the players start investigating about it thinking that it is important for the plot.